Published on February 2, 2009
about everything you always wanted to know JPEG 2000
2000 JPEG 2000 As stated by the Joint Photographic Expert Group (JPEG): “JPEG 2000 is a new image coding system 1998 that uses state-of-the-art compression MPEG 4 techniques based on wavelet technology. Its architecture should lend itself to a wide range of uses from portable digital cameras through to advanced pre-press, 1994 medical imaging and other key sectors.” MPEG 2 In 2004, JPEG 2000 was selected as the mandatory image compression format for Digital Cinema. 1992 JPEG © intoPIX
1 About JPEG 2000 A index Beneﬁts B Proﬁles by Application C How JPEG 2000 Works D JPEG 2000 Implementation E References - Glossary - Useful Links © intoPIX
2 License-Free 3 Improved Compression Efﬁciency 4 Mathematically Lossless Compression 5 Graceful Degradation 6 Scalability 7 Dynamic Bandwidth Allocation 9 JPEG 2000 Scalability and Adaptive Reception 9 Beneﬁts Robust Transmission 10 Easy Post-Production 11 Region of Interest (ROI) 12 Low Latency 13 Constant Quality through Multiple Generations 14 Encoding - Decoding Processing Power 15 Open Standard 15 Codec’s Comparison Chart 16 © intoPIX
3 License-Free The JPEG committee has stated: “It has always been a strong goal of the JPEG com- mittee that its standards should be implementable in their baseline form without payment of royalty and license fees. A [...] Agreements have been reached with over 20 large organizations holding many patents in this area to allow use of their intellectual property in connection with the standard without payment of license fees or royalties”. © intoPIX
4 Improved Compression Efﬁciency ORIGINAL IMAGE COMPRESSED WITH JPEG IMAGE COMPRESSED WITH JPEG 2000 WITH A 100 TO 1 COMPRESSION RATIO WITH A 100 TO 1 COMPRESSION RATIO © intoPIX
5 Mathematically Lossy and Visually Lossless Compression Lossless Compression At visually Lossless compression ratios, even a To maximize image quality JPEG 2000 incorporates trained eye is unable to differentiate between the a mathematically Lossless mode. original and compressed versions of an image. Mathematically Lossless compression enables A a reduction in the storage requirement of, on Visually Lossless typically achieves compression average, 2:1 while still being able to recover the ratios of 10:1 to 20:1. exact original image information. Lossy compression allows higher compression ratios This feature is extremely important in ﬁelds such i.e. 50:1 up to 100:1. In this case the compression as digital archiving, cinema acquisition and medical becomes visible but remains perfectly adequate for imaging. It is also a unique advantage in compari- e.g. web browsing. son to other popular formats like JPEG or MPEG Note: Visually Lossless and Lossy compressions both (MPEG2, MPEG4). lead to a permanent loss of data. MATHEMATICALLY MATHEMATICALLY VISUALLY LOSSLESS LOSSY LOSSLESS LOSSLESS COMPRESSION 5:1 COMPRESSION 50:1 ORIGINAL ORIGINAL COMPRESSION 2:1 DECOMPRESSION 110100100101100 110100100101100 011001011001011 011001011001011 010110110010110 010110110010110 100101100101001 100101100101001 101101001101001 101101001101001 010100101100100 010100101100100 100101101100101 100101101100101 011001100101101 011001100101101 50 MEGABITS 10 MEGABITS 1 MEGABIT 50 MEGABITS 25 MEGABITS 50 MEGABITS 010110010100101 010110010100101 100101101001010 100101101001010 © intoPIX
6 Graceful Degradation In JPEG 2000 the effect of image compression is a Contrary to JPEG and MPEG compression formats soft blur on high-frequency areas. there are no visible blocking artefacts in JPEG 2000, hence its more homogeneous or graceful image de- gradation at high compression ratios. IMAGE COMPRESSED WITH JPEG 2000 IMAGE COMPRESSED WITH JPEG 2000 WITH A 2:1 COMPRESSION RATIO WITH A COMPRESSION RATIO OF 400:1 © intoPIX
7 Quality Progression Scalability A coding format is said to be scalable when the user is able to extract multiple versions out of a single compressed ﬁle. JPEG 2000 offers resolution, color Resolution Progression component, quality and position progression scalability. A COMPRESSION Position Progression STORAGE Component Progression This scalability provides many beneﬁts, such as: Easy proxy generation Region of Interest Bandwidth optimization and adaptive transmission © intoPIX
8 EXAMPLE OF A PROGRESSION IN QUALITY 100% ACCESS 64% ACCESS 29% ACCESS 2% ACCESS © intoPIX
9 Dynamic Bandwidth Scalability and Allocation Adaptive Reception JPEG 2000 easily scales the transmitted data Using JPEG 2000 scalability over highly varia- amount to ﬁt the channel bandwidth and destination ble channels, e.g. over-IP or Wireless, provides a powerful dynamic quality allocation. resolution A Giving priority to fundamental data packets al- In a Video on Demand (VOD) service, a PDA client lows an automatic adaptation to the transmitted with a slow connection would receive a low reso- bit rate and ensures a consistent ‘best achievable lution or quality content version. quality’ for the available bandwidth. Increasing redundancy of fundamental data pac- When receiving a broadcasted signal, each receiver kets also guarantees a minimum image quality could easily use the image part corresponding to its when the signal is weak. viewing capability. In a broadcast service, a PDA user would receive the news on his PDA while his neighbor receives the same signal in full resolution on his HD TV set. © intoPIX
10 Robust Transmission JPEG 2000 intrinsic robustness prevents having Furthermore, its intra-frame nature also gives JPEG dramatic visual impact when some packets are mis- 2000 another advantage to long-GOP formats: sing or corrupted. it limits the impact of the missing or corrupt packet to a single frame. EMBEDDED ERROR OF 16 BYTES SET TO ZERO ON A JPEG 2000 IMAGE: EMBEDDED ERROR OF 16 BYTES SET TO ZERO ON A JPEG IMAGE: THE RESULT IS A HALF IMAGE CORRUPTED WITH SOFT HIGH FREQUENCIES THE RESULT IS A HALF IMAGE WITH A DRAMATIC LOSS IN COLOR QUALITY © intoPIX
11 Easy Post-Production Easy Editing Easy-Proxy Intra-frame coding enables editors to easily Resolution scalability facilitates post-production access each frame without needing to decode data ﬂow. entire groups of frames as in the case of long- From a single ﬁle depository the editors can GOP compression formats. easily extract a proxy for editing and color cor- A rection and use the full resolution image version for the rendering chain. PROXY OFF LINE EDITING e e SERVER e ORIGINAL ON LINE RENDERING e e EDL CONFORMATION © intoPIX
LOW QUALITY AREA 1212 Region of Interest (ROI) JPEG 2000 is also able to prioritize a user deﬁned area of the image, to which it will provide the full quality layer. FULL QUALITY AREA © intoPIX
13 Low Latency The intra-frame nature of JPEG2000 allows every fra- me to be encoded independently. Combined with the scalability by position, it allows latency of less than 1 frame for the full encoding-decoding process. A In comparison, inter-frame encoding formats (e.g. MPEG2, MPEG4) need to work with Groups of Pictu- res (GOP) that require a longer processing time. Low latency is a critical consideration in many appli- cations - including live broadcast, and even more so in the image compression for medical remote operation. © intoPIX
14 Constant Quality through Multiple Generations JPEG 2000 does not introduce image corruption other than that directly related to the compression process. ORIGINAL UNCOMPRESSED IMAGE IMAGE AFTER 100 SUCCESSIVE JPEG 2000 ENCODING-DECODING PASSES © intoPIX
15 Successive encoding-decoding passes are usually On the other hand, the MPEG compression-decom- required throughout the Broadcast and Digital pression process introduces additional degradation Cinema post-production processing chain. at each step, creating a cumulative deterioration of the image. Using JPEG 2000 the image quality is preserved throughout the production process. Furthermore, the wavelet based JPEG 2000 compression does A not interfere with the ﬁnal, usually DCT based, broadcast format. IMAGE QUALITY (PSNR) ORIGINAL QUALITY INITIAL COMPRESSION LOSS FINAL QUALITY DIFFERENCE MPEG ENCODING JPEG 2000 ENCODING 1 2 3 4 5 NUMBER OF ENCODING/DECODING PASSES © intoPIX
16 Encoding - Decoding Open Standard Processing Power The JPEG 2000 standard supports every resolution, color depth, number of components and frame rate. JPEG 2000 is a symmetrical compression techno- logy requiring approximately the same processing It is the image compression format most ready to power to encode or to decode at any compression address future applications. quality. In spatial imaging for instance JPEG 2000 could ad- JPEG 2000 is thus ideal for Acquisition, Storage, dress images with resolution of 10.000 by 5.000 Contribution and Archiving applications where there pixels and 4 color components (3 for visual color are as many encoders as decoders. primaries plus one for thermal capture). MPEG is an asymmetrical compression technology; its highly complex encoding and simpler decoding processes are better suited to e.g. DVD duplication or Broadcast Distribution applications where many more decoders than encoders are used. State-of-the-art JPEG 2000 codecs run on a single FPGA to provide a more cost-effective solution. © intoPIX
Codec’s JPEG MPEG2 JPEG 2000 MPEG4-AVC Comparison Chart LEGEND: MPEG4-AVC-intra Compression Efﬁciency Inter-Frame Coding intra-Frame Coding Lossless Compression POOR OR NONE Error Resilience Scalability Graceful Degradation Region of Interest MEDIUM Low Latency Multigeneration Robustness Encoder Simplicity Decoder Simplicity HIGH DVD, DVB DVD, DVB Production Still Picture Main Applications Digit. Cin., Archiving 17 © intoPIX A
18 JPEG 2000 Proﬁles High Quality Broadcast Contribution 18 Live Broadcast Streaming 19 by Application Digital Cinema Distribution 20 Digital Cinema Archiving 21 High Quality Broadcast Contribution It is essential to maintain image quality when transferring content ﬁles between Post Production facilities. PREFERRED COLOR CODE STREAM SCALABILITY RESOLUTION COMPONENT BIT DEPTH QUALITY SUBSAMPLING BIT RATE Mono 8 Math Lossless >1Gps Quality HD YUV 4:2:2 10 Near Lossless Max 1Gps Resolution 2K XYZ 4:4:4 12 Visually Lossless < 250 Mbps Position 4K RGB 16 Lossy <100 Mbps Component 2K+ RGBA 4K+ © intoPIX
19 Live Broadcast Streaming Live streaming requires very low latency and bit-rates in order to transmit video content in real time. B PREFERRED COLOR CODE STREAM SCALABILITY RESOLUTION COMPONENT BIT DEPTH QUALITY SUBSAMPLING BIT RATE Math Lossless >1Gps Near Lossless Max 1Gps Mono 8 Visually Lossless < 250 Mbps Quality HD YUV 4:2:2 10 Lossy <100 Mbps Resolution 2K XYZ 4:4:4 12 Position 4K RGB 16 Component 2K+ RGBA 4K+ © intoPIX
20 Digital Cinema Distribution Working at 4:4:4, 12 bits and at 4K resolution enables Digital Cinema Distribution to respect the pristine image quality demanded by movie Directors. PREFERRED COLOR CODE STREAM SCALABILITY RESOLUTION COMPONENT BIT DEPTH QUALITY SUBSAMPLING BIT RATE Quality Resolution Mono 8 Math Lossless >1Gps Position HD YUV 4:2:2 10 Near Lossless Max 1Gps Component 2K XYZ 4:4:4 12 Visually Lossless < 250 Mbps 4K RGB 16 Lossy <100 Mbps 2K+ RGBA 4K+ © intoPIX
21 Digital Cinema Archiving Using mathematically Lossless compression in Archiving guarantees that the highest image quality is main- tained and allows the prioritization of resolution scalability for easy ﬁle navigation and archive valorization. B PREFERRED COLOR CODE STREAM SCALABILITY RESOLUTION COMPONENT BIT DEPTH QUALITY SUBSAMPLING BIT RATE Mono 8 Quality HD YUV 4:2:2 10 Resolution 2K XYZ 4:4:4 12 Math Lossless >1Gps Position 4K RGB 16 Near Lossless Max 1Gps Component 2K+ RGBA Visually Lossless < 250 Mbps 4K+ Lossy <100 Mbps © intoPIX
22 JPEG 2000 Overview 23 Pre-processing 23 The Discrete Wavelet Transform 24 How JPEG 2000 Compression of the Wavelet Coeﬁcients 27 Works The Entropy Coding Unit 27 Rate Control 28 Data Ordering 28 Codestream Syntax 29 © intoPIX
23 JPEG 2000 Overview PRE- WAVELET COMPRESSION RATE CONTROL DATA ORDERING CODESTREAM IMAGE PROCESSING TRANSFORM Pre-processing C The pre-processing block mainly deals with color ICT (Irreversible Color Transform) conversion (or decorrelation; RGB to YUV ): RCT (Reversible Color Transform) PRE- WAVELET COMPRESSION RATE CONTROL DATA ORDERING CODESTREAM IMAGE PROCESSING TRANSFORM © intoPIX
24 The Discrete Wavelet Transform During the Wavelet Transform, image components This enables an intra-component decorrelation that are passed recursively through low pass and high concentrates the image information in a small and pass Wavelet ﬁlters. very localized area. It enables the multi-resolution image representation. PRE- WAVELET COMPRESSION RATE CONTROL DATA ORDERING CODESTREAM IMAGE PROCESSING TRANSFORM HL 2 LL 2 L1 LL 1 HL 1 HL 1 LH 2 HH 2 LL 0 H1 LH 1 HH 1 LH 1 HH 1 1ST DECOMPOSITION 2ND DECOMPOSITION © intoPIX
25 Result: 4 subbands with the upper left one containing ... Successive decompositions are applied on the low all low frequencies. frequencies. HL2 LOWER VERTICAL HL1 HL1 RESOLUTION HIGH IMAGE FREQUENCIES LH2 HH2 C HORIZONTAL DIAGONAL LH1 HH1 LH1 HH1 HIGH HIGH FREQUENCIES FREQUENCIES © intoPIX
26 + LH2 HL2 HH2 + LH1 HL1 HH1 HOW WAVELET DECOMPOSITION ACHIEVES MULTI-RESOLUTION © intoPIX
27 Compression of the Wavelet Coefﬁcients Once the Discrete Wavelet Transform (DWT) has been By itself the Wavelet Transform does not compress applied, the output is quantiﬁed. The quantized data is image data; it restructures the image information so then encoded in the Entropy Coding Unit (ECU). that it is easier to compress. COMPRESSION PRE- WAVELET ROI ENTROPY RATE CONTROL DATA ORDERING CODESTREAM IMAGE PROCESSING TRANSFORM CODING UNIT QUANT. C The Entropy Coding Unit The Entropy Coding Unit is composed of a Coefﬁ- the more probable events and longer code-words to cient Bit Modeler and the Arithmetic Coder itself. the less probable ones. The Arithmetic Coder removes the redundancy in the The Bit Modeler estimates the probability of each encoding of the data. It assigns short code-words to possible event at each point in the coding stream. e COEFICIENT ARITHMETIC QUANTIFIED COMPRESSED BIT MODEL CODING COEFICIENT IMAGE DATA © intoPIX
28 Rate Control Given a targeted bit-rate, the Rate-Control module adjusts the coding precision of each pixel (actually small groups of pixels: the code-blocks) PRE- WAVELET COMPRESSION RATE CONTROL DATA ORDERING CODESTREAM IMAGE PROCESSING TRANSFORM Data Ordering In the last ‘data ordering’ block the preferred scala- The data ordering module embeds all groups of bility (or progression order) is selected. pixels in a succession of Packets. These Packets, along with additional headers, form the ﬁnal JPEG 2000 code-stream. PRE- WAVELET COMPRESSION RATE CONTROL DATA ORDERING CODESTREAM IMAGE PROCESSING TRANSFORM © intoPIX
29 Codestream Syntax Tile-body (Data) Main Tile Tile Tile body Tile Tile Tile body P P2 P3 ... Pn header (Data) EOC header header 1 header (Data) header C Packet Code-block i Code block n SOP EPH ... header Entropic Data Entropic Data Code block inclusion Zero bit plane information Number of coding passes Data length © intoPIX
30 JPEG 2000 Implementation Implementation According to the application need JPEG 2000 will be ASICs (Application Speciﬁc Integrated Circuits) are implemented in software or hardware. usually used in large volume applications such as video surveillance. Software processing is generally used when working with still or low resolution pictures. FPGAs (Field Programmable Gate Arrays) com- bine the ﬂexibility of software processing with Hardware processing is used where image size, the power of the ASIC hardware implementa- image quality, or the number of images to process tion and are an ideal solution for lower volume per second requires higher performance. applications. Hardware solutions, including ASIC and FPGA, offer convenient processing platforms. © intoPIX
31 The intoPIX Implementation intoPIX provides the most ﬂexible and powerful range of JPEG 2000 implementations available. intoPIX efﬁcient image processing allows implemen- tation on a single FPGA. intoPIX technology currently addresses Digital Cinema and Broadcast markets. D Since 2004 intoPIX founders have been the editors of the reference open source code - OpenJPEG: www.openjpeg.org www.intopix.com © intoPIX
32 References Special issue on JPEG 2000, Signal Processing: ISO, JPEG 2000 International Standard Image Communication. Elsevier, Volume 17, Issue 1, January 2002. D. Taubman and M. Marcellin: JPEG 2000: Image compression fundamentals, Illustrations from pages 6 and 14: standards and practice, Boston, Kluwer Acade- Elephants Dream, the open source animation mic Publishers. November 2001. movie. http://www.elephantsdream.org D. Taubman: Illustrations from pages 4, 8 and 10: High performance scalable image processing DCI’s Standard Evaluation Material (StEM): with EBCOT. IEEE Trans. on Image processing. http://www.dcimovies.com July 2000. Illustrations from pages 7, 9, 12, 25 and 26 M. Rabbani: have been created using the “Lenna” test image: An overview of the JPEG 2000 still image com- http://en.wikipedia.org/wiki/Lenna pression standard, Signal processing: Image communication. 2002. © intoPIX
33 Glossary FPGA: Intra-Frame formats: Stands for “Field-Programmable Gate Array”; Coding formats that encode each frame inde- a semiconductor device containing reprogram- pendently without taking into account previous mable logic blocks. or next frames in the sequence e.g. JPEG, JPEG 2000, MPEG-4-AVC intra, etc. ASIC: Stands for “Application-Speciﬁc Integrated Cir- Inter-Frame formats: cuit”.It is an integrated circuit customized for a Coding formats that exploit the temporal redun- particular use, rather than intended for a gene- dancy of a sequence by using information appea- ral-purpose use. ring in adjacent frames e.g. MPEG2, MPEG4, MPEG-4-AVC, etc. Useful Links GOP: Stands for “Group Of Pictures” i.e. the number of pictures that an Inter-Frame format needs to Single chip JPEG 2000 codecs: www.intopix.com E perform the coding. Joint Photographic Experts Group: www.jpeg.org JPEG 2000 on Wikipedia: http://en.wikipedia.org/wiki/JPEG_2000 The open source JPEG 2000 codec: www.openjpeg.org Ofﬁcial DCI web site: www.dcimovies.com © intoPIX
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